Issued by NWS Indianapolis, IN
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000 FXUS63 KIND 201101 AFDIND AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE INDIANAPOLIS IN 701 AM EDT SAT SEP 20 2008 .AVIATION... DISCUSSION FOR 12Z TAFS. THE WEATHER MAKER FOR TODAY IS GOING TO BE AN UPPER LEVEL LOW PRESSURE IN THE MID MISSISSIPPI VALLEY. THIS LOW WILL MOVE SLOWLY NORTHWARD TOWARDS INDIANA TODAY. EARLY MORNING FOG TODAY SHOULD BURN OFF QUICKLY AND DISSIPATE AS HIGH LEVEL CLOUDS STREAM IN AHEAD OF THE SYSTEM. THERE SHOULD BE SOME SCATTERED AFTERNOON SHOWERS AND THUNDERSTORMS WITH THE UPPER LOW. WILL INCLUDE A MENTION OF CB FOR BMG AND HUF...THE SITES THAT WILL BE CLOSEST TO THE CENTER OF THE UPPER LOW AND THUS HAVE THE BEST CHANCE OF THUNDERSTORMS. FARTHER NORTH IT IS MORE LIKELY TO STAY DRY AND SO WILL NOT MENTION CB THERE. MID LEVEL CLOUDS WILL BREAK UP BETWEEN 00-06Z TONIGHT WITH CLEARING AND POSSIBLE FOG AFTER 06Z. WITH SOME UNCERTAINTY REGARDING HOW MUCH CLEARING WILL HAPPEN TONIGHT...WILL JUST TREND IN THE DIRECTION OF LIGHT FOG BUT NOT APPROACH SPECIFICS YET. && .PREV DISCUSSION... /ISSUED 220 AM EDT SAT SEP 20 2008/ DISCUSSION... FORECAST FOCUS IS ON POPS FOR TODAY/TOMORROW. MODELS IN GOOD AGREEMENT SO WL USE A BLEND. A MAV/MET BLEND WL BE USED FOR HIGHS. FOR LOWS WL BLEND BUT STICK CLOSER TO WARMER MET NUMBERS AS MAV APPEARS TO HAVE COOL BIAS BASED ON H8 TEMPS PERHAPS BECAUSE OF DEWPTS BEING TOO LOW. WEAK UPR LOW WORKING IT/S WAY N TO IL. THIS SYSTEM WL SLOWLY MV E OVR INDIANA. Q VECTORS SHOW VERY WEAK CONVERGENCE OVER INDIANA AND FRONTOGENESIS LOOKS NON EXISTANT EXCEPT AT 18Z SUN IN THE GFS. NOT MUCH IN THE WAY OF ISENTROPIC FORCING EITHER. SO ONLY FORCING AVAILABLE SEEMS TO BE THAT FROM UPR LOW COMBINED WITH DIURNAL HEATING DURING THE DAY. HOWEVER EVEN WITHOUT HEATING THIS IS CURRENTLY PRODUCING PRECIP TO OUR SW SO IT MUST BE SUFFICIENT. MUCAPES FOR SAT/SUN OVR THE AREA REACH NR 1000 IN THE AFTERNOON. WITH ALL THIS IN MIND WL GO WITH LOW CHC POPS IN THE FAR SW AND SLT CHC AROUND THERE IN CONNECTION WITH THE POSITION OF THE EDGES OF THE UPR LOW WHICH IS A BLEND OF MAV/MET. FOR TONIGHT PUT A SLT CHC IN THE FAR SW WHICH WAS SIMILAR TO THE MAV AS FORCING WANES. FOR SUNDAY WILL BRING LOW CHC W AND SLT CHC ACRS THE FA ON SUN AS GFS HAS LITTLE VORT MAX OVR THE AREA ASSOC WITH THE LOW AND PREVIOUSLY MENTIONED SLIGHTLY ENHANCED FRONTOGENESIS AROUND 18Z. DO NOT EXPECT MUCH IN THE WAY OF STORM COVERAGE EITHER DAY BUT DO THINK THERE WILL BE A COUPLE OF STORMS AROUND SO HENCE SLT CHC/LOW CHC POPS SEEMS TO BE THE BEST WAY TO EXPRESS THIS SITUATION. HIGHS TODAY AND SUNDAY AROUND 80 AND LOWS TONIGHT IN THE MID 50S TO AROUND 60 WITH SOME CLOUD COVER. AFTER SUNDAY THE UPR LOW MOVES E AND THE UPR RDG AGAIN CONTROLS THE AREA. THE FCST REMAINS DRY FROM SUN NT ON WITH THIS RELATIVELY BENIGN PATRN IN PLACE. NO CHANGES MADE TO THE EXTENDED. && .IND WATCHES/WARNINGS/ADVISORIES... NONE. && $$ AVIATION...JOHNSON PUBLIC...CP
